The present invention relates to a method of and to an apparatus for preparing concrete, plaster, mortar or like materials. For the sake of simplicity, the following description will refer to the preparation of mortar with the understanding, however, that the invention can be resorted to with equal advantage in connection with the making of plaster, concrete or other building materials wherein one or more granular or pulverulent solid constituents are mixed with one or more liquid constituents.
The aforementioned U.S. Pat. No. 4,223,996 discloses an apparatus for continuously mixing solid and liquid constituents of mortar or the like, e.g., for continuously mixing metered quantities of cement with metered quantities of water. The patented apparatus employs a horizontal housing with an inlet for the solid constituent, a feed screw which transports the solid constituent lengthwise into a mixing device, an inlet for the liquid constituent, and means for thoroughly intermixing the two constituents in the interior of the mixing device. Metering means are provided to regulate the rate of admission of solid and liquid constituents into the mixing device. As a rule, the metering means for the solid constituent constitutes or includes an intermediate chamber which is disposed between the mixing device and a first chamber receiving the solid constituent from a suitable source of supply. The patented apparatus operates quite satisfactorily. However, many presently utilized building materials should exhibit highly pronounced heat-insulating properties such as can be imparted by introduction of substantial quantities of air into the mixture of solid and liquid constituents. Heretofore known apparatus are not capable of ensuring the addition of requisite quantities of air, especially when the mixture is prepared on a continuous basis.